Neurochemical dissociation of memory systems

The administration of scopolamine, an anticholinergic drug, reduced the ability to recall and recognize stimuli presented previously--abilities thought to require declarative memory. In contrast, measures of procedural memory were unaffected by scopolamine: performance on a serial reaction time task incorporating a repeating stimulus and response sequence showed no difference in acquisition and retention of the sequence after scopolamine or saline. These results suggest that the cholinergic system is required for declarative but not procedural memory.     

TDP-43 is associated with a reduced likelihood of rendering a clinical diagnosis of dementia with Lewy bodies in autopsy-confirmed cases of transitional/diffuse Lewy body disease

Journal of Neurology - Trans-active response DNA-binding protein of 43 kDa (TDP-43) can be detected in up to 63% of autopsy-confirmed Lewy body disease (LBD) cases. It is unclear whether...     

The cognitive profile of occipital lobe epilepsy and the selective association of left temporal lobe hypometabolism with verbal memory impairment

We investigated the cognitive profile of structural occipital lobe epilepsy (OLE) and whether verbal memory impairment is selectively associated with left temporal lobe hypometabolism on [18F]‐fluorodeoxyglucose positron emission tomography (FDG‐PET). Nine patients with OLE, ages 8–29 years, completed presurgical neuropsychological assessment. Composite measures were calculated for intelligence quotient (IQ), speed, attention, verbal memory, nonverbal memory, and executive functioning. In addition, the Wisconsin Card Sorting Test (WCST) was used as a specific measure of frontal lobe functioning. Presurgical FDG‐PET was analyzed with statistical parametric mapping in 8 patients relative to 16 healthy volunteers. Mild impairments were evident for IQ, speed, attention, and executive functioning. Four patients demonstrated moderate or severe verbal memory impairment. Temporal lobe hypometabolism was found in seven of eight patients. Poorer verbal memory was associated with left temporal lobe hypometabolism (p = 0.002), which was stronger (p = 0.03 and p = 0.005, respectively) than the association of left temporal lobe hypometabolism with executive functioning or with performance on the WCST. OLE is associated with widespread cognitive comorbidity, suggesting cortical dysfunction beyond the occipital lobe. Verbal memory impairment is selectively associated with left temporal lobe hypometabolism in OLE, supporting a link between neuropsychological dysfunction and remote hypometabolism in focal epilepsy. A PowerPoint slide summarizing this article is available for download in the Supporting Information section here .     

The alien limb phenomenon

Alien limb phenomenon refers to involuntary motor activity of a limb in conjunction with the feeling of estrangement from that limb. Alien limb serves as a diagnostic feature of corticobasal syndrome. Our objective was to determine the differential diagnoses of alien limb and to determine the features in a large group of patients with the alien limb with different underlying etiologies. We searched the Mayo Clinic Medical Records Linkage system to identify patients with the diagnosis of alien limb seen between January 1, 1996, and July 11, 2011. One hundred and fifty patients with alien limb were identified. Twenty-two were followed in the Alzheimer’s Disease Research Center. Etiologies of alien limb included corticobasal syndrome (n = 108), stroke (n = 14), Creutzfeldt Jakob disease (n = 9), hereditary diffuse leukoencephalopathy with spheroids (n = 5), tumor (n = 4), progressive multifocal leukoencephalopathy(n = 2), demyelinating disease (n = 2), progressive dementia not otherwise specified (n = 2), posterior reversible encephalopathy syndrome (n = 1), corpus callosotomy (n = 1), intracerebral hemorrhage (n = 1) and thalamic dementia (n = 1). Ten of 14 cerebrovascular cases were right hemisphere in origin. All cases involved the parietal lobe. Of the 44 patients with corticobasal syndrome from the Alzheimer’s Disease Research Center cohort, 22 had alien limb, and 73 % had the alien limb affecting the left extremities. Left sided corticobasal syndrome was significantly associated with the presence of alien limb (p = 0.004). These findings support the notion that the alien limb phenomenon is partially related to damage underlying the parietal cortex, especially right parietal, disconnecting it from other cortical areas.     

Longitudinal 1H MRS changes in mild cognitive impairment and Alzheimer's disease

Magnetic resonance (MR)-based volume measurements of atrophy are potential markers of disease progression in patients with amnestic mild cognitive impairment (MCI) and Alzheimer's disease (AD). Longitudinal changes in (1)H MR spectroscopy ((1)H MRS) metabolite markers have not been characterized in MCI subjects. Our objective was to determine the longitudinal (1)H MRS metabolite changes in patients with MCI, and AD, and to compare (1)H MRS metabolite ratios and ventricular volumes in tracking clinical disease progression in AD. The neuronal integrity marker N-acetylaspartate/creatine ratio declined in MCI and AD patients compared to cognitively normal elderly. The change in (1)H MRS metabolite ratios correlated with clinical progression about as strongly as the rate of ventricular expansion, suggesting that (1)H MRS metabolite ratios may be useful markers for the progression of AD. Choline/creatine ratio declined in stable MCI, compared to converter MCI patients and cognitively normal elderly, which may be related to a compensatory mechanism in MCI patients who did not to progress to AD.     

Survival study of vascular dementia in Rochester,Minnesota

OBJECTIVE: To investigate the relationship between features and definitions of vascular dementia (VaD) and survival. DESIGN: We used the medical records linkage system of the Rochester Epidemiology Project to identify incident cases of dementia in Rochester from January 1, 1985, through December 31, 1989. Dementia and Alzheimer disease were defined using the criteria of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition. Vascular dementia was defined by ad hoc criteria, including imaging. Each patient with dementia was matched by age and sex to a referent subject free of dementia. Patients with dementia and referent subjects were followed from the onset of dementia (or index year) through death, censoring, or the end of the study. RESULTS: We included 479 patients with incident dementia and 479 referent subjects. Overall, patients with VaD had worse mortality than referent subjects (relative risk [RR], 2.7; 95% confidence interval [CI], 1.9-3.9). Among patients with VaD, those with dementia temporally related to a stroke had a worse relative mortality (RR, 4.5; 95% CI, 2.7-7.4) than those with only imaging evidence of bilateral infarctions in gray matter structures (RR, 2.4; 95% CI, 1.5-3.8). Relative mortality estimates varied by using 3 sets of published diagnostic criteria for VaD. Patients with VaD had a higher RR of death (RR, 2.7; 95% CI, 1.9-3.9) than patients with dementia overall (RR, 1.8; 95% CI, 1.6-2.1) or patients with Alzheimer disease (RR, 1.4; 95% CI, 1.2-1.7). CONCLUSIONS: The relative mortality of patients with VaD varied depending on the set of diagnostic criteria used. A temporal relationship to a stroke was the strongest predictive feature for poor survival in patients with dementia.